Abrasive disc and method of making it



Nov. 17, 1970 F. O. SHOEMAKER ABRASIVE DISC AND METHOD OF MAKING ITFiled Sept. 28, 1967 FIG. 2

INVENT FRANK O. SHOEM R BYZM HIS ATTORNEY United States Patent 3,540,163ABRASIVE DISC AND METHOD OF MAKING IT Frank 0. Shoemaker, Palos Park,Ill., assignor to The Bendix Corporation, a corporation of DelawareFiled Sept. 28, 1967, Ser. No. 671,310 Int. Cl. B2411 57/04, 11/00 U.S.Cl. 51209 3 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION Theinvention relates to grinding wheels of the type in which a flat disc ofthe abrasive material is secured to a rotatable supporting wheel, andmore particularly to reinforced abrasive discs of the nut-inserted typeand a method for making.

DESCRIPTION OF THE PRIOR ART Abrasive grinding wheels have been providedwith reinforcing members embedded therein to increase the tensilestrength and to resist the tendency to rupture under centrifugal force.With face grinding wheels it is also customary to embed securing nuts inthe abrasive material which form the anchors engaged by the clampingbolts for securing the abrasive disc to a backing plate. Abrasive discsof the nut-inserted type have been difficult to reinforce, since layersof any reinforcing material in the usable portion of the disc willchange the grinding action of the disc as the reinforcing elements areencountered through normal wear.

One prior approach has been to place the reinforcing material on theback side of the disc, next to the supporting wheel. In this area, itdoes not interfere with the grinding action, but is in the leasteffective location.

Another approach has been to place the reinforcing material at thejunction of the usable abrasive and the non-usable abrasive layer whichcontains the inserted nuts. First attempts at placing the reinforcingmaterial in this location resulted in a warping or parting of the discthrough the reinforcing section. In this location, when the disc ispressed into shape and subsequently cured the internal reinforcement isbent out of its normal plane and thus placed under stress whichultimately results, by reason of internal resiliance and memory in thereinforcing material, in either warping or cracking the abrasive disc.The bending of the reinforcing member out of its normal plane occursover the inserted nuts during the pressing operation.

Another approach has been to secure the abrasive disc to the supportingwheel by means of screws inserted through the reinforcing member andembedded into the abrasive, but the clamping pressure against thereinforcing material or the abrasive sets up stresses that tend toweaken the disc.

It can be seen that one of the major problems in abrasive discreinforcing is to place the reinforcing material at the junction of theusable and non-usable layers of abrasive material while eliminating theproblems of cracking or warping of the disc due to distortion of thereinforcing material.

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SUMMARY OF THE INVENTION The present invention presents an improvedreinforced abrasive disc having a reduced tendency to warp and crack dueto internal stresses placed on the reinforcing member during thepressing operations. An apertured reinforcing member is embedded in thedisc at the junction between the usable and non-usable layers of theabrasive disc and is entirely independent of the anchor nuts located inthe non-usable layer of the disc. The reinforcing member is oriented sothat the apertures are maintained in spaced relation over and relativeto each of the anchor nuts and in effect floats on the abrasive materialindependent of the nuts. The pressing steps in the formation thereofwill not cause a flexing or distortion of the reinforcing material overthe inserted nuts because of the apertures therein.

Thus it is an object of this invention to provide a method for placing areinforcing member at the junction of the usable and non-usable layersof abrasive material in such manner that it will accommodate itself tothe molding pressure and subsequent curing without distortion out of itsnormal plane.

A further object of this invention is to provide a reinforced abrasivedisc in which the reinforcing material is independent of the anchornuts.

DESCRIPTION OF THE DRAWING In the illustrative embodiment shown,

FIG. 1 is a section through the abrasive disc and the support 'wheel towhich it is to be attached,

FIG. 2 is a fragmentary perspective view of the abrasive disc with partsbroken away, and

FIG. 3 is a partial section view of the disc and sup porting plate inengagement.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrative embodimentshown in FIG. 1, a reinforced abrasive disc is shown generally at 2having a usable layer of abrasive material 4 and a non-usable layer ofabrasive material 6. It should be noted that the non-usable layer 6 neednot be an abrasive mixture but may be of any suitable material whichwill perform the required function and can be bonded with abrasive layer4. Attaching elements such as anchor nuts 8 and washers 10 are embeddedin the non-usable layer of abrasives. Although a flat type washer isshown, other types such as tapered cup washers have been successfullyused. Abrasive disc 2 is clamped to a supporting wheel 12 through theuse of bolts 14 which engage nuts 8.

An apertured reinforcing member 16 is embedded in the abrasive disc atthe junction between the usable layer 4 and non-usable layer 6 of theabrasive material with the cut out apertures or openings opposite eachnut 8. The reinforcing member is thus independent of nuts 8 and is notattached thereto.

The reinforcing member 16 may be an open wire mesh or other equivalentmaterial, as for instance a fiber glass mesh. In the illustrativeembodiment shown in FIG. 2 an open wire mesh material is embedded in theabrasive disc and makes a strong reinforcement by providing manyinterlocking surfaces for holding the abrasive body in place.

In a known manner, nuts 8 and washers 10 are attached in a predeterminedarrangement upon a molding plate (not shown) upon which the abrasivedisc is to be formed. A first layer of abrasive mixture is placed in themolding plate to completely surround and overlay anchor nuts 8. Holes ofgreater diameter than the corresponding anchor nuts are cut in thereinforcing memher so as to correspond to the predetermined arrangementof the anchor nuts. This apertured reinforcing member is then placedover the first layer of abrasive material and oriented so that theapertures are maintained in a spaced relation over and relative to theanchor nuts. The apertures thus allow the reinforcing member toessentially float Without distortion about the anchor nuts as theabrasive disc is compressed. A second layer of abrasive material is thenadded over the reinforcing member to a desired or predetermined height.The disc is then pressed with a press plate (not shown) to the requiredformulated density. Because the reinforcing member 16 is not secured tonuts 8 it is free to locate itself in the abrasive material withoutdistortion during the pressing operation.

The abrasive disc thus formed is hardened by curing in any known orsuitable operation.

As a consequence, the abrasive disc has a reinforcing member placed atthe junction of the usable and nonusable layers of abrasive materialwhich is freefrom internal stress and not likely to warp or crack thedisc.

It will, therefore, be appreciated that the anchor nuts 8 areindependent of the reinforcing member 16 and hence they cannot transmitany clamping stress to the reinforcing or wire mesh.

It will be observed that the abrasive body may be worn away down to thereinforcing member since there are no obstructive members or securingdevices above the reinforcing member which can interfere with thegrinding operation. This gives a maximum use of the abrasive for a giventhickness of the usable layer 4.

While the preferred form of the invention and mode of production hasbeen illustrated and described by way of example, the scope of theinvention is believed to be subject to minor changes and variations inmaterials, proportions, and minor details of manufacture withoutdeparting from the scope of the invention as defined in the followingclaims.

What I claim is:

1. A reinforced abrasive disc adapted to be attached to a rotatablesupporting wheel comprising:

a first layer of material,

a second layer of abrasive material,

attachment means embedded in said first layer adapted to attach saidabrasive disc to a supporting wheel, and

a reinforcing member independent of said attachment means at thejunction of said first and second layers of material, said reinforcingmember having apertures larger than said attachment means and disposedso that an aperture registers with each attachment means, the peripheryof said reinforcing member at' each registering aperture being held byabrasive material.

2. The method of claim 1 in which said forming of said first layercomprises the steps of:

placing a plurality of anchor means in a pre-determined arrangement on amolding plate, and

spreading a layer of material around and above said anchor means;

said reinforcing member is placed adjacent said first layer andregistered with said attachment means by:

placing an apertured reinforcing member over said first layer ofmaterial, and

orienting said reinforcing member whereby said apertures are alignedwith and maintained in a spaced relation relative to each of said anchormeans; and

said second layer is bonded to said reinforcing member and saidnon-usable layer by:

adding a layer of abrasive material over said apertured reinforcingmember,

compressing said abrasive disc to the required formulated density, and

curing said reinforced abrasive disc.

3. A method of making a reinforced abrasive disc comprising the stepsof:

forming a first layer of material having a plurality of attachment meansembedded therein:

placing a reinforcing member having apertures larger than saidattachment means adjacent said first layer so that said reinforcingmember is independent of said attachment means and an aperture registerswith said attachment means;

bonding a second layer of abrasive material to said aperturedreinforcing member and said first layer.

References Cited UNITED STATES PATENTS 1,812,076 6/1931 Beebe 51-2092,279,278 4/ 1942 Shue 51-209 2,624,986 1/1953 Loofboro 51-209 2,926,4693/ 1960 Kubsh 51 209 3,250,045 5/ 1966 Caserta 51-209 FOREIGN PATENTS388,034 2/1933 Great Britain.

ROBERT C. RIORDON, Primary Examiner DONALD G. KELLY, Assistant ExaminerUS. Cl. X.R. 51-297

